Project Summary The definition of itch as an irritating sensation that triggers the desire to scratch does not fully capture the impact on people suffering from acute and chronic itch (personal discomfort, inattention, insomnia, medical expenses, and lost work). Previous studies have highlighted the important role of TRP channels, such as TRPV1 and TRPA1, in a variety of sensory pathways including itch. In this proposal, I aim to provide a better understanding of the pathophysiology underlying itch by examining the role of the TRP channel, TRPC3, in a mouse model of allergic contact dermatitis. Previously published data from our lab found TrpC3 null mice exhibited no phenotypic differences in a variety of behavioral tests for acute pain and itch sensation. My preliminary behavioral studies have shown that TrpC3 knock out mice display greater scratching behavior in response to the mouse model of allergic contact dermatitis (ACD), termed contact hypersensitivity (CHS), when compared to wild type controls. Since TrpC3 is known to be expressed in dorsal root ganglion neurons, cholinergic neurons, glutamatergic neurons, and T cells, I hypothesize that TrpC3 antagonizes itch sensation through one of these cell types. In Aim 1, I will confirm the expression pattern of TrpC3 in the nervous system and immune system and determine whether changes in expression occur with CHS by utilizing real time PCR and in situ hybridization. Additionally, I will characterize the infiltration of immune cells in the affected skin of mice with CHS (TRPC3 KO and WT mice) through skin histology and flow cytometry. In Aim 2, I will determine whether TRPC3 modulates itch in ACD through its expression in neuronal and immune cells, using TrpC3 conditional KO mice. Specifically, I will create neuronal and immune cell TrpC3 conditional knock out mouse lines to determine which cell types require TrpC3 expression to suppress itch sensation in ACD under normal conditions by examining the scratching behavior. To target TrpC3 expression in neuronal cells, I will generate three TrpC3 conditional KO lines using Synapsin1Cre (all neurons), ChATiCre (cholinergic neurons), and VGLUT2Cre (glutamatergic neurons) genetic alleles. To target TrpC3 expression in immune cells, I will use the hematopoietic Cre line, Vav1-iCre drivers. Successful completion of the proposed aims will provide critical insight into the role of TRPC3 in antagonizing itch sensation in ACD and will propel further cellular and molecular studies to identify the pathophysiology of itch. The results of this project have the potential to impact treatment outcomes and is applicable to a significant portion of the population who suffer from ACD and chronic itch.